1. Technical Field
The embodiment described herein relates to a semiconductor integrated circuit, and more particularly, a semiconductor memory apparatus that generates a pumping voltage and a bulk voltage.
2. Related Art
In general, semiconductor memory apparatuses are supplied with an external voltage and generate an internal voltage. In the internal voltages generated by semiconductor memory apparatus, a voltage, which has higher level than the external voltage, is called a pumping voltage, and a voltage that has lower level than a ground voltage is called a bulk bias voltage (hereafter, referred to as ‘bulk voltage’).
A convention semiconductor memory apparatus that generates the pumping voltage ‘VPP’ and the bulk voltage ‘VBB’, as shown in FIG. 1, is configured to include a pumping voltage detecting unit 10, a pumping oscillator 20, a pumping charge pump 30, a bulk voltage detecting unit 40, a bulk oscillator 50, and a bulk charge pump 60. In this configuration, the pumping voltage detecting unit 10, the pumping oscillator 20, the pumping charge pump 30, the bulk voltage detecting unit 40, the bulk oscillator 50, and the bulk charge pump 60 are supplied with an external voltage as a driving voltage.
The pumping voltage detecting unit 10 detects a pumping voltage ‘VPP’ and generates a pumping detection signal ‘VPP_det’.
The pumping oscillator 20 generates a pumping oscillator signal ‘VPP_osc’ in response to the pumping detection signal ‘VPP_det’.
The pumping charge pump 30 generates the pumping voltage ‘VPP’ by performing a pumping operation in response to the pumping oscillator signal ‘VPP_osc’.
The bulk voltage detecting unit 40 detects a bulk voltage ‘VBB’ and generates a bulk detection signal ‘VBB_det’.
The bulk oscillator 50 generates a bulk oscillator signal ‘VBB_osc’ in response to the bulk detection signal ‘VBB_det’.
The bulk charge pump 60 generates the bulk voltage ‘VBB’ by performing a pumping operation in response to the bulk oscillator signal ‘VBB_osc’.
Meanwhile, as the external voltage level increases, the pumping voltage ‘VPP’ increases in voltage level by an increase range larger than a predetermined voltage increase range when one pumping operation is performed, while the bulk voltage ‘VBB’ decreases in voltage level by a decrease range larger than a predetermined voltage decrease range. That is, as the external voltage level increases, the number of times of pumping at which the pumping voltage ‘VPP’ and the bulk voltage ‘VBB’ can reach a target level decreases. As a result, as the external voltage level increases, pumping efficiency increases, but unnecessary consumption of electric current is caused when a driving ability for the voltages ‘VPP’, ‘VBB’ generated by the pumping operation exceed a predetermined driving ability.
On the other hand, as an external voltage level decreases, the pumping voltage ‘VPP’ increases in voltage level by an increase range smaller than a predetermined voltage increase range when one pumping operation is performed, while the bulk voltage ‘VBB’ decreases in voltage level by a decrease range smaller than a predetermined voltage decrease range. That is, as the external voltage level decreases, the number of times of pumping at which the pumping voltage ‘VPP’ and the bulk voltage ‘VBB’ can reach a target level increases. As a result, as the external voltage level decreases, pumping efficiency is reduced and the voltages ‘VPP’, ‘VBB’ generated by the pumping operation cannot reach a predetermined driving ability.